Cyclic AMP analog activates Na(+)-dependent inward currents in dissociated frog motoneurons

Effects of intracellular accumulation of 3',5'-cyclic adenosine monophosphate (cAMP) were studied using 3',5'-cyclic 8-bromoadenosine monophosphate (8-Br-cAMP) and forskolin on single motoneurons acutely dissociated from adult bullfrog spinal cord. 8-Br-cAMP (10(-3) M) and forskolin (1.5 x 10(-6) M) activated inward currents under K(+)-free conditions at a holding potential of -70 mV. The currents were dependent on extracellular Na+ concentration, and were never reversed within the range of membrane potentials tested (-130 to 30 mV). These results indicate that accumulation of intracellular cAMP induces Na(+)-dependent inward currents in frog motoneurons.